Just finished the game. Marvelous TD experience, really kept me on my toes with the "new paths" being added as you progress. The game did get a little slow near the later levels, but that's no problem as it was still very playable. I completed the game with 100 life so there might be room for added difficulty (maybe even more levels with increasing difficulty).

Had me on the edge of my chair the whole time. Super awesome game!